Thermochemical Processing of Algal Biomass

ABSTRACT

A thermolysis process for treating algal biomass, consisting substantially of dried algal cells, in which the algal biomass is heated from ambient to 460° C. in a flowing stream that contains one or more of carbon dioxide, acetic acid or other organic acids and that produces a condensable hydrocarbon product whose mass yield is greater than the dry, ash-free mass fraction of lipids in the starting algal biomass and whose higher enthalpy of combustion exceeds 25 MJ/kg plus a char, and a hydrocarbon-laden gaseous product. 
     In another feature, the present invention includes heating the previously dried, algal biomass in a readily available, waste acid gas, such as flue gas that is rich in carbon dioxide, or to intimately mix the algal biomass with a solid acid, such as a protonated, large pore zeolite, and then heating the mixture in a non-oxidizing sweep gas.

CROSS-REFERENCES TO RELATED APPLICATIONS

This patent application claims the benefit of provisional patentapplication No. 61/176,152, filed on May 7, 2009, which is incorporatedby reference in its entirety.

STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT

None.

REFERENCE TO A “SEQUENCE LISTING,” A TABLE, OR A COMPUTER PROGRAMLISTING APPENDIX SUBMITTED ON A COMPACT DISC AND AN INCORPORATION BYREFERENCE OF THE MATERIAL ON THE COMPACT DISC

None.

BACKGROUND OF THE INVENTION

(1) Field of the Invention

This invention relates generally to the production of fuels, chemicals,and soil amendments from biomass by means of thermolysis. Morespecifically, the invention relates to the acid-catalyzed thermolysis ofalgae.

(2) Description of the Related Art

The depletion of economically accessible petroleum and impending climatechanges that follow from the accumulation of anthropogenic carbondioxide in the atmosphere and the oceans, have motivated the search forcarbon-neutral fuels that can be produced economically and domestically.Biomass, which derives its energy content from sunlight, and whosecarbon comes from already oxidized carbon, promises to be a renewablefeedstock from which to produce liquid fuels that can substitute forfuels derived currently from petroleum.

Aquatic microalgae are widely distributed organisms that accumulatecarbon dioxide and nutrients from their environment into a material,algal biomass, which can be harvested (separated from the water). Algalbiomass grows more rapidly than do terrestrial plants, as evidenced bymuch higher areal productivities. It has long been thought that algae,which can grow very rapidly compared to terrestrial plants, might be asuitable source of biomass from which to produce liquid fuels.

A much discussed route to convert algal biomass into liquid fuels is toextract lipids (plant fats), and to convert them into either biodieselthrough transesterification with a light alcohol, or to hydrotreat thelipids to make what is termed “green” diesel. This route (oilextraction) leaves behind a large amount of protein and carbohydrate. Inprinciple, that material can be employed as an animal feed, butcomparison of the flows of mass to the fuel market with those to thefeed market suggest that the feed market would be rapidly saturated oncealgae were converted routinely to renewable fuel by that process,generating a disposal problem rather than an economic opportunity.Moreover, each of those processes typically convert only a small (and,to date, uneconomic) fraction of the heating value of the algae into theheating value of the produced fuels—either because the target fraction(e.g. the lipids) is present at low concentration in the algae, orbecause the conversion process itself is not energy efficient, or both.

A second route, steam reforming, produces synthesis gas that can beconverted, for example, by the Fischer Tropsch reaction, into fuel rangehydrocarbons. However, this route requires an investment in energy (boththe steam reforming reaction and the Fischer-Tropsch reactions aretypically carried out at high pressure), and is not very carbonefficient because some of the input carbon is diverted back to carbondioxide or light hydrocarbons, which are frequently disposed by flaring.

A third route, hydrothermal processing, produces a high yield of liquidhydrocarbon products, but also a large quantity of hydrocarbon-ladenwater that can present a disposal cost, and a dilution of some of thedesired products.

A fourth route, pyrolysis, is very general but has previously beencarried out at high temperatures that exacerbate the corrosivity of theproducts and necessitates the use of expensive, refractory reactors.

Other processes have also been explored, but none has yet offeredcompelling financial economics or attractive carbon efficiencies,despite research campaigns that seem to recrudesce about every thirtyyears. What is needed in the art is that the algal biomass-derived feedstocks be amenable to further refining together with conventional fuelfeed stocks to take advantage of the existing capital investment inpetroleum refining, and to make the algal biomass-derived fuel fungiblewith conventional petroleum-derived fuels. It is further desirable thatany solid residuum from the production of the algal biomass-derived,liquid fuel feedstock also have economic value, for example as a solidfuel or as a soil amendment where minerals and heteroatoms (e.g., N, P)can be returned to the biosphere, albeit possibly in a different venuefrom which they came.

BRIEF SUMMARY OF THE INVENTION

A thermolysis process for treating algal biomass, consistingsubstantially of dried algal cells, in which the algal biomass is heatedfrom ambient to 460° C. in a flowing stream that contains one or more ofcarbon dioxide, acetic acid or other organic acids and that produces acondensable hydrocarbon product whose mass yield is greater than thedry, ash-free mass fraction of lipids in the starting algal biomass andwhose higher enthalpy of combustion exceeds 25 MJ/kg plus a char, and ahydrocarbon-laden gaseous product.

Another feature of the method of the present invention is heating thepreviously dried, algal biomass in a readily available, waste acid gas,such as flue gas that is rich in carbon dioxide, or to intimately mixthe algal biomass with a solid acid, such as a protonated, large porezeolite, and then heating the mixture in a non-oxidizing sweep gas.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

FIG. 1 shows a temperature profile, illustrated by a solid curve,employed in TGA/GC/MS experiments detailed in Examples 1 and 2,discussed below.

FIG. 2 shows chromatograms obtained at the sequence of the indicatedsample temperatures (100° C., 290° C., 460° C.) in Example 1 during thethermolysis of a sample of algal biomass heated along the ramp shown inFIG. 1 in a flowing stream consisting of 66.7 mol % CO₂ and 33.3 mol %N₂.

FIG. 3 shows an expanded view of a chromatogram obtained in Example 1 ofthe gas stream produced during the TGA/GC-MS experiment, sampled at 50°C.

FIG. 4 compares the expanded chromatograms obtained in Example 1 at 100°C. during the thermolysis of a sample of algal biomass heated along thetemperature trajectory shown in FIG. 1 in a flowing stream consistingeither of pure N₂, as illustrated by a light weight curve or of 66.7 mol% CO₂ and 33.3 mol % N₂, as illustrated by a heavy weight curve.

FIG. 5 shows chromatograms obtained in Example 1 at the indicatedsequence of sample temperatures (100° C., 290° C. and 560° C.) duringthe thermolysis of a sample of algal biomass intimately mixed withH-ZSM-5 heated according to the temperature ramp shown in FIG. 1 in aflowing stream consisting of 66.7 mol % CO₂ and 33.3 mol % N₂. Theeffluent stream from the sample was analyzed with the aid of a GC/MS atthe end of the soak periods or when the temperature first reached theindicated value during the ramp periods.

FIG. 6 compares chromatograms obtained in Example 2 at 50° C. heatedaccording to the temperature trajectory shown in FIG. 1 during thethermolysis in a flowing stream consisting of 66.7 mol % CO₂ and 33.3mol % N₂ of a sample of algal biomass, as illustrated by a heavy curve,and another sample that had been previously, intimately mixed withH-ZSM-5, as illustrated by a light curve.

FIG. 7 is a schematic diagram of a process in which the thermolysis ofalgal biomass is integrated with the flue gas and waste heat from anindustrial process.

FIG. 8 shows the temperature trajectory followed and the evolution ofthermolysis products from the experiment described in Example 3,discussed below.

DETAILED DESCRIPTION OF THE INVENTION

The process of the present invention includes thermolysis that can becarried out at temperatures less than 460° C. when assisted by thepresence of carbon dioxide or a solid acid catalyst. In one advantageousembodiment, dry biomass consisting substantially of algal cells iscontacted in the absence of additional catalysts with a stream of hotgas containing carbon dioxide. In another advantageous embodiment, drybiomass is intimately mixed with a solid acid catalyst, such as H-ZSM-5,for example, and then contacted with a stream of hot gas. The hot gasmay be carbon dioxide, diluted carbon dioxide, or any other suitable hotgas. The different advantageous embodiments provide a process thatevolves thermolysis products at temperatures below 100° C. and even aslow as 50° C. in the presence of a solid acid catalyst. As will be seenfrom the examples below, the thermolysis products span compositions thatare different from those seen in the pyrolysis of cellulosic biomass.The high heating value of the oily product is an advantageous result inview of much lower values typically found for pyrolysis products fromcellulose (Table 1).

TABLE 1 Comparison of the specific heating values of petrofuels and somebiofuels: Material HHV/MJ kg⁻¹ Algae derived thermolysis-oil^(c) 36Crude petroleum 45-48 Jet fuel (minimum) 43 Refined biodiesel 38Wood-derived py-oil ~20 

Because both CO₂-assisted and solid acid-catalyzed thermolysis of algalbiomass occur at comparatively low temperatures, a process deployingeither embodiment can be integrated with an industrial facility toemploy heat that would otherwise be wasted and/or deoxygenated flue gasfrom a combustion process that would otherwise be vented. A schematic ofa process flow is shown in FIG. 7. Algae are grown in helioreactors(738), harvested continuously via flocculation (734) and pressed toremove bulk water (736). The partially dried algae are conveyed to adrying kiln (730) that can be heated using hot flue gas from theindustrial partner. The temperature and flow rate of the flue gas islowered by mixing a stream of gas from the flue (724), throttled byvalve (728) and mixing the hot gas with ambient air whose inlet flowrate is controlled by the air mixing valve (732). The gases are drawn bythe action of the induction fan (718) through the drying kiln andthrough the particle separator (720) and then a cooled in heat exchanger722. The now dry algae are conveyed to Kiln 710 where they are treatedwith hot, gas that has been deoxygenated by reaction with thermolysischar in kiln (714) and cooled in heat exchanger (712). The treated charis accumulated in storage vessel (716). The volatile products ofthermolysis are condensed by passage through heat exchanger (702) andthe condensibles are collected in storage vessel (704). The char iscollected in vessel 706 before it is transferred to the inlet of thedeoxygenation kiln (704). The hot thermolysis gas and the volatileproducts are transported through the kilns and heat exchangers by meansof the induction fan (708), which also transports the noncondensableproducts of thermolysis to a flare (726) where they can be safelycombusted. Because this process reuses heat from the industrial partner,there could be an allowance for the carbon dioxide that would have beenproduced had, instead, a carbon-based fuel been combusted to supply thatheat.

Example 1

A small quantity of unwashed algal biomass, about 30 mg was placed inthe pan of a thermal gravimetric balance. The gas outlet of the TGA wasconnected via heat-traced stainless steel tubing to a 6-port samplingvalve mounted on the inlet to an HP5890 gas chromatograph equipped witha capillary column and an HP mass selective detector. Either N₂ or amixture of 66.7 mol % CO₂ plus 33.3% N₂ was flowed through the heatedchamber at about 100 ml/min. The sample was then heated according to thetrajectory shown in FIG. 1. When the sample had been heated to thetemperatures indicated in FIG. 2, constant volume samples of theeffluent stream were injected into the GC/Ms through the approximately 1ml loop attached to the 6-port sampling valve. The identity of theeluted compounds was determined by comparing the cracking pattern of themass spectrogram of each peak against spectra drawn from the library ofthe instrument.

FIG. 1 depicts the weight losses in Example 1 by a sample of algaeheated in either pure nitrogen, as illustrated by a short dashed curveor in a mixture consisting of 66.7% CO₂ and 33.7% N₂, as illustrated bya long dashed curve. As indicated in FIG. 1, the sample heated in thegas stream that contained carbon dioxide lost more weight than did thesample heated in the stream containing only dinitrogen. Buoyancy effectsare suppressed in this presentation of the data because we normalizedthe initial weights of the samples (also measured in the reaction gases)to 100%.

The effluent stream obtained in Example 1 from the sample was analyzedwith the aid of a GC/MS at the end of the soak periods or when thetemperature first reached the indicated value during the ramp periods.

At the end of the first 50° C. soak period, the gas stream consisted ofthe compounds listed in Table 2, which eluted through the GC at timesand in amounts illustrated in FIG. 3. In particular, four compounds,which appeared at this low temperature at significantly greaterabundance when the sweep gas contained CO₂ than when the sweep gas waspure N₂, include indole, methylindole, trimethyl-bicyclo[3.1.1]heptanes,and propylcyclohexanol.

In Table 2, shown below, are compounds identified in the GC/MSchromatogram of the TGA effluent from an algae sample treated in 60ml/min CO₂—F30 ml/min N₂ flow gas sampled at 50° C. In FIG. 3, thenumbers labeling the peaks correspond to the compounds listed in Table2, depicted below.

Peak # RT/min Compounds Formula 301 4.681 to 4.754 PyrrolidinedioneC₄H₅NO₂ 302 5.177 to 5.236 Butenoic acid, ethyl ester C₆H₁₀O₂ 303 5.604to 5.691 Indole C₈H₇N 304 6.041 to 6.119 Methyl-1H-Indole C₉H₉N 3057.806 to 7.833 TrimethylBicyclo[3.1.1]heptane, C₁₀H₁₈ 306 7.961 to 7.997Propylcyclohexanol C₉H₁₈O

Identifications of the compounds represented by peaks in thechromatographic analysis of the TGA effluent for this sample atsuccessive temperatures along the trajectory shown in FIG. 1 arepresented in Tables 3-9.

Table 3, shown below, is a GC/MS chromatogram of the TGA effluent froman algae sample treated in 60 ml/min CO₂+30 ml/min N₂ flow gas sampledat 100° C. Entries in italics (Peaks 407-410) describe compounds thatdid not appear at 50° C. In FIG. 4, the numbers labeling the peakscorrespond to the compounds listed in Table 3, depicted below.

Peak # RT/min Compounds Formula 401 4.681 to 4.754 2,5-PyrrolidinedioneC₄H₅NO₂ 402 5.177 to 5.236 2-Butenoic acid, ethyl ester C₆H₁₀O₂ 4035.604 to 5.691 Indole C₈H₇N 403 6.041 to 6.119 Methyl-1H-Indole C₉H₉N405 7.806 to 7.833 trimethyl-bicyclo[3.1.1]heptane C₁₀H₁₈ 406 7.961 to7.997 2-Propylcyclohexanol C₉H₁₈O 407 4.789 to 4.8441,2,4-Triazine-3,5(2H,4H)-dione C ₃ H ₃ N ₃ O ₂ 408 6.491 to 6.5322,4,6-trimethyl-Benzonitrile, C ₁₀ H ₁₁ N 409 6.536 to 6.5632,7-dimethyl-Indolizine, C ₁₀ H ₁₁ N 410 7.955 to 8.0013,7,11,15-Tetramethyl-2-hexadecen-1-ol C ₂₀ H ₄₀ O

Table 4, shown below, is a GC/MS chromatogram of the TGA effluent froman algae sample treated in 60 ml/min CO₂+30 ml/min N₂ flow gas sampledat 200° C. Entries in italics (Peaks 11-12) describe compounds that didnot appear at 100° C.

Peak # RT/min Compounds Formula 1 4.681 to 4.754 2,5-PyrrolidinedioneC₄H₅NO₂ 2 5.177 to 5.236 2-Butenoic acid, ethyl ester, (E)- C₆H₁₀O₂ 35.604 to 5.691 Indole C₈H₇N 4 6.041 to 6.119 Methyl-1H-Indole C₉H₉N 57.806 to 7.833 trimethyl-,Bicyclo[3.1.1]heptane C₁₀H₁₈ 6 7.961 to 7.9972-Propylcyclohexanol C₉H₁₈O 7 4.789 to 4.8441,2,4-Triazine-3,5(2H,4H)-dione C₃H₃N₃O₂ 8 6.491 to 6.5322,4,6-trimethyl-Benzonitrile, C₁₀H₁₁N 9 6.536 to 6.563 Indolizine,2,7-dimethyl- C₁₀H₁₁N 10 7.955 to 8.001 3,7,11,15-Tetramethyl-2- C₂₀H₄₀Ohexadecen-1-ol 11 5.037 to 5.142 Dodecane C ₁₂ H ₂₆ 12 5.933 to 5.9791,2-dihydro-1,1,6-trimethyl C ₁₃ H ₁₆ Naphthalene

Table 5, shown below, is a GC/MS chromatogram of the TGA effluent from asample of algal biomass treated in 60 ml/min CO₂+30 ml/min N₂ flow gassampled at 290° C. Entries in italics (Peaks 13-15) describe compoundsthat did not appear at 200° C.

Retention Peak # Time/min Compounds Formula 1 4.681 to 4.7542,5-Pyrrolidinedione C₄H₅NO₂ 2 5.177 to 5.236 2-Butenoic acid, ethylester, (E)- C₆H₁₀O₂ 3 5.604 to 5.691 Indole C₈H₇N 4 6.041 to 6.119Methyl-1H-Indole C₉H₉N 5 7.806 to 7.8332,6,6-trimethyl-bicyclo[3.1.1]heptane,, C₁₀H₁₈ 6 7.961 to 7.9972-Propylcyclohexanol C₉H₁₈O 7 4.789 to 4.8441,2,4-Triazine-3,5(2H,4H)-dione C₃H₃N₃O₂ 8 6.491 to 6.532 Benzonitrile,2,4,6-trimethyl- C₁₀H₁₁N 9 6.536 to 6.563 Indolizine, 2,7-dimethyl-C₁₀H₁₁N 10 7.955 to 8.001 3,7,11,15-Tetramethyl-2-hexadecen-1-ol C₂₀H₄₀O11 5.037 to 5.142 Dodecane C₁₂H₂₆ 12 5.933 to 5.979 Naphthalene,1,2-dihydro-1,1,6-trimethyl C₁₃H₁₆ 13 6.064 to 6.109 1H-Indole,3-methyl- C ₉ H ₉ N 14 6.310 to 6.341 Dodecane C ₁₂ H ₂₆ 15 7.274 to7.324 Dodecane C ₁₂ H ₂₆

Table 6, shown below, is a GC/MS chromatogram of the TGA effluent froman algae sample treated in 60 ml/min CO₂+30 ml/min N₂ flow gas sampledat 460° C. Entries in italics (Peaks 13, 16-38) describe compounds thatdid not appear at 290° C.

Peak # RT/min Compounds Formula 3 5.604 to 5.691 Indole C₈H₇N 5 7.806 to7.833 2,6,6-trimethyl- C₁₀H₁₈ Bicyclo[3.1.1]heptane 6 7.961 to 7.9972-Propylcyclohexanol C₉H₁₈O 13 6.064 to 6.109 3-methyl-1H-Indole C₉H₉N16 1.383 to 1.501 Pentane C ₅ H ₁₂ 17 2.515 to 2.606 Toluene C ₇ H ₈ 182.656 to 2.707 Cyclooctane C ₈ H ₁₆ 19 2.711 to 2.7972,4-dimethyl-Heptane C ₉ H ₂₀ 20 4.417 to 4.485 3-methyl-Phenol, C ₇ H ₈O 21 4.517 to 4.567 Cyclododecane C ₁₂ H ₂₄ 22 4.567 to 4.617 Dodecane C₁₂ H ₂₆ 23 5.049 to 5.085 1-methyl-2-octyl- C ₁₂ H ₂₄ Cyclopropane 245.085 to 5.122 Dodecane C ₁₂ H ₂₆ 25 5.536 to 5.568 1-Tridecene C ₁₃ H₂₆ 26 5.581 to 5.604 Dodecane C ₁₂ H ₂₆ 27 5.827 to 5.863 4-Decene C ₁₀H ₂₀ 28 6.004 to 6.032 2-Tetradecene C ₁₄ H ₂₈ 29 6.036 to 6.063Dodecane C ₁₂ H ₂₆ 30 5.931 to 5.963 Dodecane C ₁₂ H ₂₆ 31 6.291 to6.314 Dodecane C ₁₂ H ₂₆ 32 6.314 to 6.341 Dodecane C ₁₂ H ₂₆ 33 6.441to 6.468 1-Pentadecene C ₁₅ H ₃₀ 34 6.473 to 6.500 Dodecane C ₁₂ H ₂₆ 356.859 to 6.882 1-Hexadecene C ₁₆ H ₃₂ 36 6.882 to 6.909 Dodecane C ₁₂ H₂₆ 37 7.273 to 7.371 Dodecane C ₁₂ H ₂₆ 38 7.401 to 7.428 Z-5-NonadeceneC ₁₉ H ₃₈

Table 7, shown below, is a GC/MS chromatogram of the TGA effluent froman algae sample treated in 60 ml/min CO₂+30 ml/min N₂ flow gas sampledwhen cooled to 350° C. Entries in italics (Peaks 39-46) describecompounds that did not appear at 460° C.

Peak # RT/min Compounds Formula 3 5.621 to 5.661 Indole C₈H₇N 13 6.064to 6.109 3-methyl-1H-Indole C₉H₉N 33 6.445 to 6.463 1-Pentadecene C₁₅H₃₀34 6.472 to 6.495 Dodecane C₁₂H₂₆ 35 6.850 to 6.882 1-Hexadecene C₁₆H₃₂36 6.882 to 6.909 Dodecane C₁₂H₂₆ 37 7.273 to 7.371 Dodecane C₁₂H₂₆ 387.401 to 7.428 Z-5-Nonadecene C₁₉H₃₈ 39 3.852 to 3.980 Phenol C ₆ H ₆ O40 4.303 to 4.380 2-methyl-Phenol C ₇ H ₈ O 41 4.407 to 4.5264-methyl-Phenol C ₇ H ₈ O 42 4.685 to 4.730 2,5-Pyrrolidinedione C ₄ H ₅NO ₂ 43 4.835 to 4.885 2,4-dimethyl-Phenol C ₈ H ₁₀ O 44 4.903 to 4.9714-ethyl-Phenol C ₈ H ₁₀ O 45 7.250 to 7.273 3-Heptadecene, (Z)- C ₁₇ H₃₄ 46 7.396 to 7.437 3,7,11-trimethyl-1- C ₁₅ H ₃₂ O Dodecanol

Example 2

Algal biomass was comminuated with a commercial sample of H-ZSM-5powder. A small quantity of that mixture or the algal biomass alone,about 30 mg in each case, was placed in the pan of a thermal gravimetricbalance. The gas outlet of the TGA was connected via heat-tracedstainless steel tubing to a 6-port sampling valve of an HP5890 gaschromatograph equipped with a capillary column and an HP mass selectivedetector. The samples were heated according to the temperaturetrajectory shown in FIG. 1 while contacted with a 90 ml/min flow of N₂.When the sample had been heated to 50° C., 100° C., 200° C., 290° C. and460° C., constant volume samples of the effluent stream were injectedinto the GC/Ms through an approximately 1 ml loop attached to the 6-portsampling valve. The full chromatograms are shown in FIG. 5 at theindicated temperatures. The identity of the eluted compounds wasdetermined by comparing the cracking pattern of the mass spectrogram ofeach peak against spectra drawn from the library of the instrument.

At the end of the first 50° C. soak period, the gas stream consisted ofthe compounds listed in Table 8. All twelve of the peaks listed in Table8 appeared at this low temperature only when the sample contained theacid catalyst, in this example.

In Table 8, shown below, are compounds identified in the GC/MSchromatogram shown in FIG. 6 of the TGA effluent in Example 2 from analgal biomass and algal biomass+zeolite samples treated in 90 ml/min ofN₂, sampled at 50° C. In FIG. 6, the numbers labeling the peakscorrespond to the compounds listed in Table 8, depicted below.

Peak #: RT (min) Compounds Formula 601 4.345 to 4.545 Phenol, 4-methyl-C₇H₈O 602 4.691 to 4.754 2,5-Pyrrolidinedione C₄H₅NO₂ 603 4.841 to 4.8952,4-dimethyl-Phenol C₈H₁₀O 604 4.900 to 4.973 4-ethyl-Phenol C₈H₁₀O 6055.623 to 5.664 Indole C₈H₇N 606 6.064 to 6.105 4-methyl-1H-Indole, C₉H₉N607 6.856 to 6.883 Cyclohexadecane C₁₆H₃₂ 608 6.883 to 6.956 DodecaneC₁₂H₂₆ 609 7.081 to 7.115 Dodecane C₁₂H₂₆ 610 7.256 to 7.2793-Heptadecene, (Z)- C₁₇H₃₄ 611 7.279 to 7.306 Dodecane C₁₂H₂₆ 612 7.816to 7.838 Phytol C₂₀H₄₀O

Table 9, shown below, lists compounds identified in the GC/MSchromatogram of the TGA effluent from an algal biomass and algalbiomass+zeolite samples treated in 90 ml/min of N₂, sampled at 100° C.Lines in italics (Peaks 13-14) describe compounds that did not appear at50° C.

Peak RT (min) Compounds Formula 1 4.345 to 4.545 Phenol, 4-methyl- C₇H₈O2 4.691 to 4.754 2,5-Pyrrolidinedione C₄H₅NO₂ 3 4.841 to 4.895 Phenol,2,4-dimethyl- C₈H₁₀O 4 4.900 to 4.973 Phenol, 4-ethyl- C₈H₁₀O 5 5.623 to5.664 Indole C₈H₇N 6 6.064 to 6.105 1H-Indole, 4-methyl- C₉H₉N 7 6.856to 6.883 Cyclohexadecane C₁₆H₃₂ 8 6.883 to 6.956 Dodecane C₁₂H₂₆ 9 7.081to 7.115 Dodecane C₁₂H₂₆ 10 7.256 to 7.279 3-Heptadecene, (Z)- C₁₇H₃₄ 117.279 to 7.306 Dodecane C₁₂H₂₆ 12 7.816 to 7.838 Phytol C₂₀H₄₀O 13 7.392to 7.433 1-Heptene, 2-isohexyl- C ₁₄ H ₂₈ 6-methyl- 14 7.956 to 7.9883,7,11,15-Tetramethyl-2- C ₂₀ H ₄₀ O hexadecen-1-ol

Table 10, shown below, lists compounds identified in the GC/MSchromatogram of the TGA effluent from an algae and algae+zeolite samplestreated in 90 ml/min of N₂, sampled at 200° C. Lines in italics (Peaks15-19) describe compounds that did not appear at 100° C.

Peak Retention #: Time (min) Compounds Formula 1 4.345 to 4.545 Phenol,4-methyl- C₇H₈O 2 4.691 to 4.754 2,5-Pyrrolidinedione C₄H₅NO₂ 3 4.841 to4.895 Phenol, 2,4-dimethyl- C₈H₁₀O 4 4.900 to 4.973 Phenol, 4-ethyl-C₈H₁₀O 5 5.623 to 5.664 Indole C₈H₇N 6 6.064 to 6.105 1H-Indole,4-methyl- C₉H₉N 7 6.856 to 6.883 Cyclohexadecane C₁₆H₃₂ 8 6.883 to 6.956Dodecane C₁₂H₂₆ 9 7.081 to 7.115 Dodecane C₁₂H₂₆ 10 7.256 to 7.2793-Heptadecene, (Z)- C₁₇H₃₄ 11 7.279 to 7.306 Dodecane C₁₂H₂₆ 12 7.816 to7.838 Phytol C₂₀H₄₀O 13 7.392 to 7.433 1-Heptene, 2-isohexyl-6-methyl-C₁₄H₂₈ 14 7.956 to 7.988 3,7,11,15-Tetramethyl-2- C₂₀H₄₀O hexadecen-1-ol15 5.182 to 5.218 1,4:3,6-Dianhydro-.alpha.-d- C6H8O4 glucopyranose 165.241 to 5.273 Phenol, 2-ethyl-6-methyl- C9H12O 17 5.296 to 5.332Benzene, 1-ethyl-4-methoxy- C9H12O 18 7.606 to 7.652 1-Octadecene C18H3619 7.652 to 7.697 Dodecane C ₁₂ H ₂₆

Table 11, shown below, lists compounds identified in the GC/MSchromatogram of the TGA effluent from an algal biomass and algalbiomass+zeolite samples treated in 90 ml/min of N₂, sampled at 290° C.Lines in italics (Peaks 20-29) describe compounds that did not appear at200° C.

Peak RT (min) Compounds Formula 1 4.419 to 4.519 Phenol, 4-methyl- C₇H₈O2 4.664 to 4.746 2,5-Pyrrolidinedione C₄H₅NO₂ 3 4.841 to 4.895 Phenol,2,4-dimethyl- C₈H₁₀O 4 4.900 to 4.973 Phenol, 4-ethyl- C₈H₁₀O 5 5.623 to5.664 Indole C₈H₇N 6 6.064 to 6.105 1H-Indole, 4-methyl- C₉H₉N 8 6.883to 6.907 Dodecane C₁₂H₂₆ 9 7.081 to 7.115 Dodecane C₁₂H₂₆ 10 7.256 to7.279 3-Heptadecene, (Z)- C₁₇H₃₄ 11 7.279 to 7.306 Dodecane C₁₂H₂₆ 127.816 to 7.838 Phytol C₂₀H₄₀O 13 7.392 to 7.433 1-Heptene,2-isohexyl-6-methyl- C₁₄H₂₈ 14 7.956 to 7.9883,7,11,15-Tetramethyl-2-hexadecen-1-ol C₂₀H₄₀O 15 5.182 to 5.2181,4:3,6-Dianhydro-.alpha.-d-glucopyranose C₆H₈O₄ 16 5.237 to 5.269Phenol, 2-ethyl-6-methyl- C₉H₁₂O 17 5.296 to 5.332 Benzene,1-ethyl-4-methoxy- C₉H₁₂O 18 7.606 to 7.652 1-Octadecene C₁₈H₃₆ 19 7.652to 7.697 Dodecane C₁₂H₂₆ 20 1.585 to 2.190 Acetic acid C ₂ H 4 O ₂ 212.435 to 2.499 Pyridine C ₅ H 5 N Pyrrole C ₄ H 5 N 22 2.513 to 2.563Toluene C ₇ H 8 23 2.631 to 2.708 Propanoic acid, 2-oxo-, methyl ester C₄ H 6 O ₃ 24 4.746 to 4.773 Benzene, (2-methyl-1-propenyl)- C ₁₀ H 12 255.933 to 5.979 Naphthalene, 1,2-dihydro-1,1,6-trimethyl C ₁₃ H 16 266.493 to 6.520 Ethaneperoxoic acid, 1-cyano-1-(2-methyl C ₁₂ H 13 NO ₃27 6.529 to 6.570 1H-Indole, 2,5-dimethyl- C ₁₀ H 11 N 28 6.857 to 6.8843-Hexadecene, (Z)- C ₁₆ H 32 7-Hexadecene, (Z)- C ₁₆ H 32 29 7.207-7.2303-Heptadecene, (Z)- C ₁₇ H 34

Table 12, shown below, lists compounds identified in the GC/MSchromatogram of the TGA effluent from an algae and algae+zeolite samplestreated in 90 ml/min of N₂, sampled at 460° C. Entries in italics (Peaks30-44) describe compounds that did not appear at 390° C.

Peak RT (min) Compounds Formula 1 4.419 to 4.519 Phenol, 4-methyl- C₇H₈O5 5.623 to 5.664 Indole C₈H₇N 6 6.064 to 6.105 1H-Indole, 4-methyl-C₉H₉N 10 7.253 to 7.275 3-Heptadecene, (Z)- C17H34 11 7.279 to 7.306Dodecane C₁₂H₂₆ 12 7.816 to 7.838 Phytol C₂₀H₄₀O 14 7.956 to 7.9883,7,11,15-Tetramethyl-2- C₂₀H₄₀O hexadecen-1-ol 18 7.606 to 7.6521-Octadecene C₁₈H₃₆ 19 7.652 to 7.697 Dodecane C₁₂H₂₆ 22 2.499 to 2.581Toluene C₇H₈ 30 1.908 to 1.999 Benzene C ₆ H ₆ 31 3.141 to 3.181Ethylbenzene C ₈ H ₁₀ 32 3.186 to 3.241 p-Xylene C ₈ H ₁₀ 33 3.341 to3.400 Styrene C ₈ H ₈ Xylene C ₈ H ₁₀ 34 3.796 to 3.832 Benzene,1-ethyl-2-methyl- C ₉ H ₁₂ 35 3.987 to 4.023 Benzene, 1,3,5-trimethyl- C₉ H ₁₂ 36 4.319 to 4.355 Benzene, 1-propynyl- C ₉ H ₈ 37 4.787 to 4.887Benzyl nitrile C ₈ H ₇ N 38 4.901 to 4.937 Benzene, (1-methyl-2- C ₁₀ H₁₀ cyclopropen-1-yl)- 39 4.937 to 4.969 2-Methylindene C ₁₀ H ₁₀ 405.078 to 5.110 Dodecane C ₁₂ H ₂₆ 41 5.110 to 5.160 Naphthalene C ₁₀ H ₈42 5.656 to 5.711 Naphthalene, 2-methyl- C ₁₁ H ₁₀ 43 6.311 to 6.343Dodecane C ₁₂ H ₂₆ 44 6.470 to 6.493 Dodecane C ₁₂ H ₂₆

Table 13, shown below, lists compounds identified in the GC/MSchromatogram of the TGA effluent from an algal biomass and algalbiomass+zeolite samples treated in 90 ml/min of N₂, sampled at 350° C.Entries in italics (Peaks 46-51) described compounds that did not appearat 460° C.

Peak RT (min) Compounds Formula 1 4.419 to 4.519 Phenol, 4-methyl- C₇H₈O2 4.664 to 4.746 2,5-Pyrrolidinedione C₄H₅NO₂ 3 4.841 to 4.895 Phenol,2,4-dimethyl- C₈H₁₀O 4 4.900 to 4.973 Phenol, 4-ethyl- C₈H₁₀O 5 5.623 to5.664 Indole C₈H₇N 6 6.064 to 6.105 1H-Indole, 4-methyl- C₉H₉N 10 7.253to 7.275 3-Heptadecene, (Z)- C₁₇H₃₄ 11 7.279 to 7.306 Dodecane C₁₂H₂₆ 127.816 to 7.838 Phytol C₂₀H₄₀O 13 7.392 to 7.433 1-Heptene,2-isohexyl-6-methyl- C₁₄H₂₈ 14 7.956 to 7.9883,7,11,15-Tetramethyl-2-hexadecen-1-ol C₂₀H₄₀O 41 5.110 to 5.160Naphthalene C₁₀H₈ 42 5.656 to 5.711 Naphthalene, 2-methyl- C₁₁H₁₀ 453.852 to 3.984 Phenol C₆H₆O 46 5.184 to 5.2391,4:3,6-Dianhydro-.alpha.-d-glucopyranos C ₆ H ₈ O ₄ Benzofuran,2,3-dihydro- C ₈ H ₈ O 47 5.339 to 5.398 Benzenepropanenitrile C ₉ H ₉ N48 6.126 to 6.158 Amobarbital C ₁₁ H ₁₈ N ₂ O ₃ 49 6.176 to 6.212Pentobarbital C ₁₁ H ₁₈ N ₂ O ₃ 50 6.444 to 6.467 1-Pentadecene C ₁₅ H₃₀ 51 6.472 to 6.499 Dodecane C ₁₂ H ₂₆

Example 3

A preparatory scale reactor constructed from a vertical alumina tube (7cm OD) placed in the center of an electrically heated tube furnace wasloaded with approximately 200 g of algal biomass and then connected to agas cylinder. The gas cylinder permitted the interior of the verticalalumina tube to be swept with carbon dioxide that had bubbled at ambienttemperature through an aqueous solution of 5% acetic acid and then in tothe reactor tube at a flow rate of 0.2 standard L/min. The effluent fromthe reactor was directed into a glass receiver whose outside walls werecooled in an ice bath. The temperature of the reactor tube was ramped to400° C., as shown in FIG. 8, and maintained at that temperature for 100minutes, with CO₂ flowing at 45 ml/min. Approximately 100 ml ofoily/waxy material was collected, from which was estimated a mass yieldof 27 wt % in the oil fraction. During the heating, the nature of theeffluent from the heated tube changed as indicated in Table 14.

Table 14, shown below, shows changes in the character of the effluentfrom the preparatory scale reactor as the reaction temperatureincreases.

Marker shown in FIG. 8 Character of the reactor effluent stream 802Smoke starts to appear 804 Smoke stops evolving 806 Clear liquidcommences to collect in the chilled receiver vessel. 808 White smokeappears in the receiver and flows out of the receiver 810 Yellow smokestarts to fill the receiver and a yellow wax collects on the sides ofthe receiver 812 An orange liquid starts to collect in the receiver as adense vapor 814 A thick, dark brown tar collects in the rceiver

Analysis of the initial algal biomass showed a lipid content of 3.5%.Subsequently, the enthalpy of combustion of the oil/wax was measured ina bomb calorimeter and found to be 36 MJ/kg, with a sulfur content of0.22%.

There are many advantages to the method of the present invention. Thisinvention is directed at obtaining feed stocks from which to prepareliquid fuels from a renewable source, such as algal biomass that growsrapidly, with little impact on available water or food resources.

The different advantageous embodiments provide a process that convertsbiomass, consisting substantially of whole, dry algae cells, into anoily material that exhibits a heating value approximating that ofpetroleum, along with a solid carbonaceous char, a hydrocarbon-laden gasstream, and an aqueous stream that contains polar organic compounds.

In an advantageous embodiment, the algal biomass can be processed intothe feedstock with a net decrease in carbon dioxide emissions, forexample by using carbon dioxide and heat from an existing process thatwould otherwise be wasted. The process of the present invention convertsa broad range of microalgae and the co-harvested micro-organisms,referred to as algal biomass, into three products: a hydrocarbon-ladengas, a carbonaceous char, a new oily material that exhibits many of thecharacteristics of crude petroleum, and an aqueous stream that dissolvespolar compounds. The process produces significant quantities of oilyproduct from algal biomass that does not contain high concentrations oflipids. Therefore, the process can be applied even to algal biomass thathas not been selected or nurtured to generate lipids.

The thermolysis produces a range of products that commence to evolve atunexpectedly low temperatures—as low as 50° C., i.e., hundreds ofdegrees lower than the temperatures at which cellulosic biomass must beheated to produce pyrolysis oils. The temperature range of thethermolysis of the algal biomass is low enough that the process can becarried out using waste heat generated by other industrial processes,for example cement manufacturing. The low temperature processing confersan economic advantage and offers a possible route to so-called carboncredits for the partner industry. Moreover, the oily material derivedfrom the algae has an unexpectedly high enthalpy of combustion—around 36MJ/kg, which approaches the heating value of petroleum (ca. 44 MJ/kg)and is about twice as large as the heating value of pyrolysis oilsderived from cellulosic biomass (ca. 20 MJ/kg).

In addition, the algal biomass-derived oily material can constitute morethan 15 wt % of the original, ash-free, dry weight of the algae, evenfor starting material that contains less than 5 wt % lipids. Finally,the composition of the algal biomass-derived oily material suggests thatit would be amenable to subsequent processing along side conventionalpetroleum-derived gas oil, unlike pyrolysis oils derived from cellulosicbiomass. For example, the elemental analyses performed, and the heatingvalue mentioned above, provide an inference that the oily material fromthe described thermolysis of algal biomass presents feweroxygen-containing components than does cellulose-derived pyrolysis oil,along with a concentration of sulfur that is low enough to be consideredfor blending into low sulfur feed stocks, yet high enough to maintainthe activity of conventional hydroprocessing catalysts.

These conventional hydroprocessing catalysts can be used in conventionalrefinery processes to hydro-upgrade the oily material, for example toremove nitrogen, metals, and oxygen heteroatoms.

1. A thermolysis process for treating algal biomass, consistingsubstantially of dried algal cells, in which the algal biomass is heatedfrom ambient to 460° C. in a flowing stream that contains one or more ofcarbon dioxide, acetic acid or other organic acids and that produces acondensable hydrocarbon product whose mass yield is greater than thedry, ash-free mass fraction of lipids in the starting algal biomass andwhose higher enthalpy of combustion exceeds 25 MJ/kg plus a char, and ahydrocarbon-laden gaseous product.
 2. A thermolysis process for treatingalgal biomass, consisting substantially of dried algal cells, in whichthe algal biomass is intimately mixed with a solid acid catalyst and isheated from ambient to 460° C. in a flowing gas stream that produces acondensable hydrocarbon product whose mass yield is greater than thedry, ash-free mass fraction of lipids in the starting algal biomass andwhose higher enthalpy of combustion exceeds 25 MJ/kg, plus a char, and ahydrocarbon-laden gaseous product.
 3. The process of claim 1 in whichthe thermolysis products are collected fractionally as the temperatureof the biomass increases.
 4. The process of claim 2 in which thethermolysis products are collected fractionally as the temperature ofthe biomass increases.
 5. The process of claim 1 in which the condensedproduct stream contains: a. Indole; b. Methyl indole; c. Succinimide; d.Propylcyclohexanol; e. Dodecane; f. Dodecene; g. Tridecene; h.Pentadecene; i. Heptadecene; j. Nonadecene; and k. at least 0.1 wt %sulfur.
 6. The process of claim 2 in which the condensed product streamcontains: a. Methylphenol; b. Indole; c. Methylindole; d.Dimethylphenol; e. Ethylphenol; f. Succinimide; g. Propylcyclohexanol;h. Trimethylbicycloheptane; i. Succinimide; j. Propylcyclohexanol; k.Trimethylbicycloheptane; I. Dodecane; m. Pentadecene; n. Heptadecene; o.Phytol; p. Amobarbital; q. Pentobarbital; and r. at least 0.1 wt %sulfur.
 7. The process of claim 1 in which condensed product fractionsproduced at temperatures less than or equal to 50° C. contain: a.Indole; b. Methylindole; c. Succinimide; d. Propylcyclohexanol; and e.Trimethylbicycloheptane
 8. The process of claim 2 in which condensedproduct fractions produced at temperatures less than or equal to 50° C.contain: a. Methylphenol; b. Indole; c. Methylindole; d. Dimethylphenol;e. Ethylphenol; f. Succinimide; g. Propylcyclohexanol; h.Trimethylbicycloheptane; i. Dodecane; j. Heptadecene; and k. Phytol 9.The process of claim 1 in which the temperature of the algal biomass israised using waste heat from an industrial process.
 10. The process ofclaim 2 in which the temperature of the algal biomass is raised usingwaste heat from an industrial process.
 11. The process of claim 1 inwhich the sweep gas comes from the flue gas of another industrialprocess and is deoxygenated by reacting it with the char produced in theprocess of claim
 1. 12. The process of claim 2 in which the sweep gascomes from the flue gas of another industrial process and isdeoxygenated by reacting it with the char produced in the process ofclaim
 2. 13. The process integration of claim 9 in which the partnerindustrial process receives greenhouse gas credits in proportion to thefuel whose heat has been used to thermolyze the algal biomass.
 14. Theprocess integration of claim 10 in which the partner industrial processreceives greenhouse gas credits in proportion to the fuel whose heat hasbeen used to thermolyze the algal biomass.
 15. The process integrationof claim 11 in which the partner industrial process receives greenhousegas credits in proportion to the fuel whose heat has been used tothermolyze the algal biomass.
 16. The process integration of claim 12 inwhich the partner industrial process receives greenhouse gas credits inproportion to the fuel whose heat has been used to thermolyze the algalbiomass.